To service a refrigeration circuit, such as used for food refrigeration, air conditioning, and assorted cooling purposes wherein a refrigerant is compressed, expanded, and condensed it is usually required to remove the refrigerant. Further, refrigerant can become contaminated by foreign matter within the refrigeration circuit, or by condensing moisture, and while oil is commonly mixed with the refrigerant for lubrication purposes the ratio of refrigerant to oil may adversely change over a period of time and it is often desirable to change the refrigerant to improve the operation efficiency.
When servicing a refrigeration circuit it has been the practice for the refrigerant to be vented into the atmosphere, the apparatus serviced and repaired, the circuit is then evacuated by a vacuum pump, and recharged with refrigerant. This procedure has now become unacceptable for environmental reasons in that the discharge of refrigerant into the atmosphere is now considered to produce serious contamination. Also, the cost of refrigerant is now becoming an important factor with respect to service costs, and such a waste of refrigerant, which could be reprocessed, is no longer acceptable.
In view of the adverse environmental impact of venting refrigerant into the atmosphere refrigerant recovery and evacuation systems have been devised to overcome such problems wherein the recovered refrigerant is stored for disposal. Such a system is shown in the assignee's U.S. Pat. No. 4,261,178.
Further, a system has been proposed for the servicing of refrigeration circuits wherein the refrigerant may be removed from the circuit and stored, and the circuit recharged with fresh refrigerant, such system using common components, as disclosed in U.S. Pat. No. 4,363,222 assigned to the assignee.
When servicing refrigeration circuits utilizing compressors the refrigerant includes lubricating oil, and upon evacuating the circuit lubricating oil will be removed. Heretofore, it has not been possible to accurately determine the extent of such oil loss during servicing, and it is possible that the previous haphazard procedures for servicing compressor type refrigeration circuits may result in either too much or too little oil within the circuit resulting in compressor damage or inefficiency of operation. Previously, refrigerant evacuation and charging systems have not been capable of closely monitoring lubricating oil removal and recharging.
It is an object of the invention to provide a fully portable refrigeration circuit refrigerant recovery and recharging system which is suitable for servicing refrigeration circuits on site, such as automobile air conditioning systems, wherein the refrigerant is removed from the circuit, and wherein recharging is accomplished, the various cycles and sequences of operation being automatically accomplished by a electronic control.
Another object of the invention is to provide a refrigerant recovery and charging system wherein lubricating oil is separated from the recovered refrigerant, and during recharging a predetermined amount of oil is injected into the refrigeration circuit.
A further object of the invention is to provide a refrigerant recovery and charging system wherein the recovered refrigerant is filtered and purified on site and utilized to recharge the refrigeration circuit from which it has been withdrawn.
Yet another object of the invention is to provide a refrigerant recovery and recharging system whose operation and cycling is automatically controlled through a microprocessor and wherein recovered refrigerant is processed, purified and utilized to recharge the circuit, and wherein fresh refrigerant may be added to the reprocessed refrigerant to make up for any difference between the amount of reprocessed refrigerant available and that required to properly charge the circuit.
In the practice of the invention a manifold conduit system communicates with the high and low sides of the refrigeration circuit to be serviced. A recovery compressor or pump withdraws refrigerant from the circuit through a filter, evaporator and oil separator. The refrigerant, in liquid form, is stored within a reservoir or receiver, and the receiver may constitute a disposal container, but preferably, constitutes a reservoir communicating with a metering pump which has an outlet in selective communication with a refrigerant purifier whereby the liquid refrigerant may be removed from the reservoir and passed through the purifier. It is possible to cycle the refrigerant through the purifier to produce a refined, clean refrigerant, and upon valve operation the metering pump will draw refrigerant from the purifier and its associated circuit for charging into the manifold conduit system and the refrigeration circuit. A supply of fresh refrigerant selectively communicates with the metering pump to make up any lack of refrigerant existing in the purifier circuit, and the metering pump assures that the refrigeration circuit is fully charged.
Further, metered oil injection means communicate with the manifold conduit system whereby, during recharging, a predetermined amount of lubricating oil may be introduced into the refrigeration circuit. The oil separator is capable of determining the amount of oil removed from the recovered refrigerant, and the amount of oil injected into the manifold conduit for recharging purposes is determined by the amount of oil removed during recovery.
As the system of the invention utilizes a plurality of components which are interconnected by conduits and electrically operated valves the circuit utilizes pressure switches and other known control instruments which supply information to a preprogrammed microprocessor control wherein the various cycles and sequences of operation may be automatically controlled, and will be indicated to the operator. The automatic controls inform the operator through a display the various stages of operation occurring, or required, and the electronic control substantially eliminates human error with respect to sequence of system operation.